/*
 * Copyright 2007 The Closure Compiler Authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.javascript.jscomp.type;

import static com.google.javascript.rhino.jstype.JSTypeNative.ARRAY_TYPE;
import static com.google.javascript.rhino.jstype.JSTypeNative.NO_OBJECT_TYPE;
import static com.google.javascript.rhino.jstype.JSTypeNative.NULL_TYPE;
import static com.google.javascript.rhino.jstype.JSTypeNative.NULL_VOID;
import static com.google.javascript.rhino.jstype.JSTypeNative.NUMBER_STRING_BOOLEAN_SYMBOL;
import static com.google.javascript.rhino.jstype.JSTypeNative.OBJECT_TYPE;
import static com.google.javascript.rhino.jstype.JSTypeNative.VOID_TYPE;

import com.google.common.base.Function;
import com.google.common.collect.ImmutableMap;
import com.google.javascript.rhino.Node;
import com.google.javascript.rhino.jstype.FunctionType;
import com.google.javascript.rhino.jstype.JSType;
import com.google.javascript.rhino.jstype.JSTypeRegistry;
import com.google.javascript.rhino.jstype.ObjectType;
import com.google.javascript.rhino.jstype.Visitor;
import java.util.Map;
import javax.annotation.CheckReturnValue;

/**
 * A reverse abstract interpreter (RAI) for specific closure patterns such as
 * {@code goog.isDef}.
 *
 */
public final class ClosureReverseAbstractInterpreter
    extends ChainableReverseAbstractInterpreter {

  /**
   * For when {@code goog.isObject} returns true. This includes functions, but
   * not {@code null}.
   */
  private final Visitor<JSType> restrictToObjectVisitor =
      new RestrictByTrueTypeOfResultVisitor() {
        @Override
        protected JSType caseTopType(JSType topType) {
          return getNativeType(NO_OBJECT_TYPE);
        }

        @Override
        public JSType caseObjectType(ObjectType type) {
          return type;
        }

        @Override
        public JSType caseFunctionType(FunctionType type) {
          return type;
        }
      };

  /**
   * For when {@code goog.isObject} returns false.
   */
  private final Visitor<JSType> restrictToNotObjectVisitor =
      new RestrictByFalseTypeOfResultVisitor() {

        @Override
        public JSType caseAllType() {
          return typeRegistry.createUnionType(
              getNativeType(NUMBER_STRING_BOOLEAN_SYMBOL), getNativeType(NULL_VOID));
        }

        @Override
        public JSType caseObjectType(ObjectType type) {
          return null;
        }

        @Override
        public JSType caseFunctionType(FunctionType type) {
          return null;
        }
      };

  /** Functions used to restrict types. */
  private final Map<String, Function<TypeRestriction, JSType>> restricters;

  public ClosureReverseAbstractInterpreter(final JSTypeRegistry typeRegistry) {
    super(typeRegistry);
    this.restricters =
        new ImmutableMap.Builder<String, Function<TypeRestriction, JSType>>()
            .put(
                "isDef",
                p -> {
                  if (p.outcome) {
                    return getRestrictedWithoutUndefined(p.type);
                  } else {
                    return p.type != null
                        ? getNativeType(VOID_TYPE).getGreatestSubtype(p.type)
                        : null;
                  }
                })
            .put(
                "isNull",
                p -> {
                  if (p.outcome) {
                    return p.type != null
                        ? getNativeType(NULL_TYPE).getGreatestSubtype(p.type)
                        : null;
                  } else {
                    return getRestrictedWithoutNull(p.type);
                  }
                })
            .put(
                "isDefAndNotNull",
                p -> {
                  if (p.outcome) {
                    return getRestrictedWithoutUndefined(getRestrictedWithoutNull(p.type));
                  } else {
                    return p.type != null
                        ? getNativeType(NULL_VOID).getGreatestSubtype(p.type)
                        : null;
                  }
                })
            .put("isString", p -> getRestrictedByTypeOfResult(p.type, "string", p.outcome))
            .put("isBoolean", p -> getRestrictedByTypeOfResult(p.type, "boolean", p.outcome))
            .put("isNumber", p -> getRestrictedByTypeOfResult(p.type, "number", p.outcome))
            .put("isFunction", p -> getRestrictedByTypeOfResult(p.type, "function", p.outcome))
            .put(
                "isArray",
                p -> {
                  if (p.type == null) {
                    return p.outcome ? getNativeType(ARRAY_TYPE) : null;
                  }

                  Visitor<JSType> visitor =
                      p.outcome ? restrictToArrayVisitor : restrictToNotArrayVisitor;
                  return p.type.visit(visitor);
                })
            .put(
                "isObject",
                p -> {
                  if (p.type == null) {
                    return p.outcome ? getNativeType(OBJECT_TYPE) : null;
                  }

                  Visitor<JSType> visitor =
                      p.outcome ? restrictToObjectVisitor : restrictToNotObjectVisitor;
                  return p.type.visit(visitor);
                })
            .build();
  }

  @Override
  public FlowScope getPreciserScopeKnowingConditionOutcome(Node condition,
      FlowScope blindScope, boolean outcome) {
    if (condition.isCall() && condition.hasTwoChildren()) {
      Node callee = condition.getFirstChild();
      Node param = condition.getLastChild();
      if (callee.isGetProp() && param.isQualifiedName()) {
        JSType paramType =  getTypeIfRefinable(param, blindScope);
        Node left = callee.getFirstChild();
        Node right = callee.getLastChild();
        if (left.isName() && "goog".equals(left.getString()) &&
            right.isString()) {
          Function<TypeRestriction, JSType> restricter =
              restricters.get(right.getString());
          if (restricter != null) {
            return restrictParameter(param, paramType, blindScope, restricter,
                outcome);
          }
        }
      }
    }
    return nextPreciserScopeKnowingConditionOutcome(
        condition, blindScope, outcome);
  }

  @CheckReturnValue
  private FlowScope restrictParameter(
      Node parameter,
      JSType type,
      FlowScope blindScope,
      Function<TypeRestriction, JSType> restriction,
      boolean outcome) {
    // restricting
    type = restriction.apply(new TypeRestriction(type, outcome));

    // changing the scope
    if (type != null) {
      return declareNameInScope(blindScope, parameter, type);
    } else {
      return blindScope;
    }
  }

  private static class TypeRestriction {
    private final JSType type;
    private final boolean outcome;

    private TypeRestriction(JSType type, boolean outcome) {
      this.type = type;
      this.outcome = outcome;
    }
  }
}
